| |
Many of you might have heard about a recent
published report on the result of a prostate
cancer prevention study done through
the Southwest Oncology Group (SWOG) and sponsored by the National
Cancer Institute (NCI). This scientific report was published in
the July 17, 2003 issue of the New England Journal of Medicine
(NEJM) and was publicized through a news conference by the NCI.
Our interpretation of the findings is discussed here.
What is this drug called?
The name is Finasteride (Proscar®) and it is the first
drug found to reduce the risk of prostate cancer. This drug was
approved by the FDA in 1992 at a 5 mg dose for treating an enlarged
prostate condition or BPH, and a few years later, it was approved
at a 1 mg dose to treat male pattern baldness.
How long was this study?
This study was set to be a 10-year trial and was originally scheduled
to end in May 2004. On March 3, 2003, the Data and Safety Monitoring
Committee advised that the trial be closed
early. The recommendation came because
data already collected were sound, and the conclusions were extremely
unlikely to change with the addition of more data, the committee
determined. The NEJM article was based on findings involving about
half the study participants. Despite enrolling 18,882 men, the study
was not large enough or long enough to determine if Finasteride
improved overall survival. This would likely require 15 years of
observation and 57,000 participants. However, the investigators
will continue to follow these men and see what happens with them.
What were the main findings?
Of the 55 year-old men with normal digital (finger) rectal examinations
and PSA readings of less than 3.0 ng/ml who were randomized to receive
finasteride, about 18.4% had prostate cancer when they were
biopsied after completing seven years on the drug.
Of the men who had been taking placebo
for the trial period, 24.4% had prostate cancer proven by biopsy
at the end of the period. That's an absolute reduction of 6%, meaning
a relative risk reduction of 25%.
Overall, 6.4% of the finasteride patients
were found to have high-grade cancer.
Among the placebo patients, 5.1% had high-grade tumors. That's
an absolute difference of 1%, but with the huge numbers of men taking
part in the study, the researchers accept that the finding is real.
The drug apparently worked for men at low risk for prostate cancer
as well as those at high risk.
Are the findings surprising?
Many prostate cancer experts were surprised that finasteride profoundly
reduced cancer in these men. Previous studies of the drug in patients
who already had prostate cancer did not show much use for the drug.
Which finding was troubling?
The appearance of high-grade cancer was a particularly worrisome
finding since it was seen more in the finasteride group. With an
absolute difference of 1%, this suggests that if men take finasteride
to prevent prostate cancer, there is a one in 100 chance that they
will develop a dangerous (high-grade) form of prostate cancer. Part
of the problem with the study result is that the cancers being prevented
by finasteride are not the cancers that are of the greatest concern
to doctors (urologists) treating prostate cancer.
What were other findings in this
study?
The patients taking finasteride had reduced risk of urinary problems
but a higher incidence of sexual side-effects including impotence.
So there were positive effects as well as tradeoffs.
From the facts of this study, how
would we advise our patients?
The study provides the first clear evidence that prevention of prostate
cancer can be done. It provides us a lot more facts than we had
before, but it doesn't make it any easier to advise our patients
what to do. There are still some important unanswered questions,
especially regarding side-effects, whether it can benefit men at
increased risk, especially African-Americans, who are twice as likely
as white men to die of prostate cancer, and the mechanism by which
men taking the drug develop high-grade cancers.
We think that we are able to tell men who are on finasteride now
for control of benign prostatic hyperplasia (enlarged prostate or
BPH) that they do not have to change their medication. They should
be monitored closely if they have prostate changes. Similarly, men
using the low 1 mg dose for baldness can safely continue this drug
with similar monitoring.
For patients with a family history of prostate cancer, it is also
reasonable to consider taking finasteride as a preventive measure.
As with any medical treatment, a decision to take finasteride is
a individual one in which the benefits and risks must be considered.
We encourage you to discuss your particular circumstance with your
doctor.
* This information
is not intended to substitute for a consultation with a urologist.
It is offered to educate patients on the basis of urological conditions
in order to get the most out of their office visits and consultations.
Please see our web page disclaimer
for addition information.
|
|
